6                 A fire in an enclosed space burns with the aid of reflected radiation that preheats the fuel, making ignition much easier and flames spreading more quickly.

(A) flames spreading

(B) flame spreads

(C) flames are caused to spread

(D) causing flames to spread（D）

(E) causing spreading of the flames

我想知道，能不能把a看成 making ignition much easier and (making) flames spreading more quickly 

不平衡啊。 前面是doing + n而making flames spreding 就是doing + 非名次性结构了（好像不能算是动名词，我也不知道该叫啥，呵呵）